1. Field of the Invention
The present disclosure relates to rotorcraft. More specifically, the present disclosure relates to rotor assemblies having automatic blade folding systems.
2. Description of Related Art
Rotorcraft such as, but not limited to, helicopters include a plurality of rotor blades that are used to generate the lift and effectuate the primary flight control of the craft. When the rotorcraft is not in use, it can be desired to move or fold the blades of the rotorcraft to a non-flight position. In such a non-flight position, the span of the blades can be moved to a position over the body of the craft to reduce the footprint of the rotorcraft.
Many manual and automatic blade folding systems have been proposed. Some prior systems require large hydraulic pressure cylinders mounted within the main rotor shaft to drive all rotor blades to the full lead position. Unfortunately, the large hydraulic pressure cylinders add undesired weight to the rotorcraft. Further, driving the rotor blades to the full lead position can place undesired strain on various elastomeric bearings, which can reduce the service life of such bearings. Moreover, the large hydraulic pressure cylinders systems require continuous pressurization, which has proven to be prone to leakage.
In order to overcome the strain placed on the elastomeric bearings some prior systems have included a pitch restraint system. These pitch restraint systems prevent the blade from dropping to the ground during the fold by reacting the torsional loads generated during the fold cycle. One prior pitch restraint system requires hydraulically or mechanically locking a plurality of control servos for each blade after driving all of the rotor blades to the full lead position. Unfortunately, these systems again add undesired weight and have not proven effective at reducing the loads on the elastomeric bearings.
Accordingly, there is a need for automatic blade folding systems and rotorcraft having such systems that overcome one or more of the aforementioned and other deleterious effects of the prior art blade folding systems.